In a typical inkjet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol, a polyhydric alcohol or mixtures thereof.
An inkjet recording element typically comprises a support having on at least one surface thereof at least one ink-receiving layer. The ink-receiving layer is typically either a porous layer that imbibes the ink via capillary action, or a polymer layer that swells to absorb the ink. Transparent swellable hydrophilic polymer layers do not scatter light and therefore afford optimal image density and gamut, but may take an undesirably long time to dry. Porous ink-receiving layers are usually composed of inorganic or organic particles bonded together by a binder. During the inkjet printing process, ink droplets are rapidly absorbed into the coating through capillary action, and the image is dry-to-touch right after it comes out of the printer. Therefore, porous coatings allow a fast “drying” of the ink and produce a smear-resistant image. However porous layers, by virtue of the large number of air-particle interfaces, scatter light that may result in lower densities of printed images.
Furthermore, inkjet prints prepared by printing onto inkjet recording elements are subject to environmental degradation. They are especially vulnerable to damage resulting from contact with water and atmospheric gases such as ozone. The damage resulting from the post-imaging contact with water can take the form of water spots resulting from deglossing of the top coat, dye smearing due to unwanted dye diffusion, and even gross dissolution of the image recording layer. Ozone can bleach inkjet dyes resulting in loss of density. To overcome these deficiencies, inkjet prints are often laminated. However, lamination is expensive as it requires a separate roll of material.
Efforts have been made to avoid lamination and yet provide protected inkjet prints by providing an inkjet receiver having an uppermost fusible ink-transporting layer and an underlying ink-retaining layer.
Inkjet elements having a fusible porous upper layer are known in the art. Fusing the upper layer after printing the image has the advantage of providing a protective overcoat for water and stain resistance and reducing light scatter for improved image quality.
For example, U.S. Pat. Nos. 4,785,313 and 4,832,984 relate to an inkjet recording element comprising a support having thereon a porous fusible, ink-transporting layer and a swellable polymeric ink-retaining layer, wherein the ink-retaining layer is non-porous.
EP 858, 905A1 relates to an inkjet recording element having a porous fusible ink-transporting outermost layer formed by heat sintering thermoplastic particles, and an underlying porous layer to absorb and retain the ink applied to the outermost layer to form an image. The underlying porous ink-retaining layer is constituted mainly of refractory pigments. After imaging, the outermost layer is made non-porous.
EP 1,188,573 A2 relates to a recording material comprising in order: a sheet-like paper substrate, at least one pigment layer coated thereon, and at least one sealing layer coated thereon. Also disclosed is an optional dye-trapping layer present between the pigment layer and the sealing layer.
U.S. Pat. No. 6,497,480 to Wexler discloses inkjet media comprising both a fusible ink-transporting layer and a dye-trapping layer. A base layer and/or a porous under the fusible layer may be employed to absorb ink carrier-liquid fluid.
Protective overcoats and crosslinked overcoats for recording elements are also known in the art. For example, U.S. Pat. No. 6,436,617 relates to protective overcoats for photographic image elements comprising water-dispersible latex particles, which particles comprise an epoxy material and a thermoplastic acid polymer, a water-soluble hydrophilic polymer and a hydrophobically modified associative thickener. The hydrophilic polymer is substantially washed out during photographic processing facilitating the coalescence of the hydrophobic materials. Another driving force for this coalescence is the elevated temperature drying associated with photoprocessing.
U.S. Pat. No. 6,548,182 relates to an inkjet recording material wherein the coating comprises a water-soluble polymer having a plurality of carboxyl groups and a water-soluble oxazoline group as a crosslinking agent.
It is an object of this invention to provide a porous inkjet recording element which can be printed with inkjet inks and fused to provide high-density images. It is another object of the invention to provide a protective uppermost pigment-trapping layer that is thermally fusible and thereby can be rendered water and stain resistant.